The invention relates to the packaging of somewhat fragile equipment, such as portable electronic apparatus, and in particular to high density, lightweight, physically protective, electronic packaging with enhanced capability for cooling.
The technology of arranging and supporting electronic components for use as a functional apparatus has come to be referred to in the art as packaging. Fragile equipment and electronic apparatus packaging generally provides a housing for the signal processing elements or devices that permits them to operate in the designed manner while still protecting them from potentially detrimental hazards encountered in conditions of use. As the equipment and the electronic apparatus becomes smaller and more portable, the density and sensitivity of the devices require greater cooling ability and physical protection while the applications in which use will take place, such as cellular phones and laptop computers require ever diminishing weight and physical volume together with increased hazard protection. Portable devices are more difficult to cool, more complex to wire; they can be placed near radiating equipment and they are subject to being dropped. The packaging must typically protect, have highly efficient cooling and having electrical shielding capability.
In cooling, heat that is locally generated at a signal processing device must be transferred to the ambient outside the structure. As device density and performance go up, the heat transfer criteria become more difficult to satisfy without there also being some transfer of heat from one closely packed device that may affect another.
The current goals in portable electronic apparatus are directed to confining the total weight of the apparatus including the housing or case to less than 4 lbs., while permitting ever denser assemblies of heat generating elements. To achieve such a low weight goal, new materials and packaging relationships will be needed.
In packaging design it is becoming very difficult to meet all the conflicting criteria with the conventional properties of materials and structures.
Packaging efforts in the prior art have been principally directed toward handling such individual aspects as overall heat dissipation from the entire structure and electrical shielding.
In U.S. Pat. Nos. 4,783,721, 4,879,632 and 4,920,574 a metal bellows structure accommodates expansion differences between heat generating semiconductor chip devices and a common heat transfer fluid conduit but at the expense of the addition of significant structure.
In U.S. Pat. No. 5,029,638 the increased area property of a permeable material is employed in fins in a heat exchanger that improves conduction of the heat from the chip to the heat transfer fluid thereby reducing need to accommodate as much expansion. The progress provided by U.S. Pat. No. 5,029,638, in cooling alone, involves significant additional structure which may not be tolerable if there are other and conflicting requirements in the direction of compactness and weight.
Permeable materials, that is materials that provide additional surface area and permit liquid and gasseous coolant to flow through them, have been further employed in the art.
In European patent EP 48,488 a layered housing is employed with a material called a metal fleece for the purpose of enhancing shielding.
In European Patent EP0559092 of McLellan a metal foam is used in a semiconductor device heat sink to enhance the radiation properties of the heat sink area.
In IBM TDB Vol.22, No.11, April 1980, page 5095, a porous metal is used as a heat transfer enhancer.
In U.S. Pat. No. 4,408,255 layers of steel wool are added to metal shielding layers for cooling purposes.
The invention provides lightweight packaging of portable electronic apparatus by using the combined structural properties of an enclosure, that houses the intertwined heat producing electronic signal devices of the apparatus, to provide coolant movement and direction, locally selectable physical protection and shock resistance and electrical shielding.
It achieves the packaging benefits by having;
a laminated enclosure member structure that has an internal device supporting lamination and an external wear resistant lamination on each side of a layer of a material that has the combined physical properties of selectably interrelated coolant permeability and density, non-corrosiveness and electrical conductivity;
heat generating signal processing devices mounted on the internal lamination;
positioned holes through the laminations on each side of the permeable material layer that provide entrance, exit and directing openings for a coolant fluid, including air,that is brought in from the outside, and, propelling the coolant at least convectionally, by the heat from the signal processing devices and additionally by a separate fan located in the enclosure, so that the heated coolant is exhausted to the outside.
Localized shock resistance is imparted by selective change in the density of the permeable layer.